Ventilation of rotor end coils of turbogenerators



Sept- 1933- c. .1. FECHHEIMER 1,927,390

VENTILATION OF ROTOR END COILS OF TURBOGENERATORS Filed Dec. 19, 1930 2SheetsSheet l WITNE E5 INVENTOR wg 9wv Carl J. fEchhe/mer (Q72 3WATTORNEY 19, 1950 2 Sheets-Sheet 2 w 9 W m m R NQH N m E J V C T N m w wv hk M Y M aw r n d a w a C M an 9.

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1 i .hk W\. m? \N T Sept. 26, 1933. c. .1. FECHHEIMER VENTILATION OFROTOR END COILS OF TURBOGENERATORS Filed Dec.

Patented Sept. 26, 1933 UNITED STA VENTILATION OF ROTOR END COILS OFTURBOGENERATORS Carl J, Fechheimer, Pittsburgh, Pa., assignor toWestinghouse Electric & Manufacturing Company, a corporation ofPennsylvania Application December 19, 1930 Serial No. 503,429

4 Claims.

My invention relates to high-speed or steamturbine-driven generators,commonly called turbo-generators,- and it has particular relation to theVentilation or cooling of the long end turns of the rotor field windingsof large machines of this class.

Owing to the rather long lengths that are used in the coil-ends ofturbo-rotors, especially for two-pole machines, but also for largefour-pole machines, and especially for the lower frequencies, such asand 60 cycles, high temperatures occur at or near the middle portions ofthe circumferential coil-end lengths, because the heat cannot escapeotherwise than by conduction to the retaining rings or along the copperof the coilends to the core of therotor. I In the past, an attempt hasbeen made to over come this difficulty by drilling holes through theretaining rings which surround the coil-ends and retain them againstcentrifugal forces. It has been found, however, that very little benefitwas obtained by this expedient.

According to my present invention, I have found, by exhaustive tests,that ample cooling vcanbe obtained by reducing the volume of air thatpasses over the coil-ends, but greatly in creasing the .velocity'of thisair, so that the amount of heat interchanged per unit area of ex-.posed'coil-ends, for each degree of temperature difference, is greatlyincreased, notwithstanding the reduced total volume of air.

taining ring 8.

With the foregoing and other objects in view, my invention consists inthe combinations and structures hereinafter described and claimed andillustrated in the accompanying drawings, where- Figure 1 is alongitudinal sectional view of a part of a turbo-generator rotor memberembodying my invention,

Fig. 2 is a transverse sectional view thereof on the plane indicatedby-the line 11-11 on Fig. 1,

Fig. 3 is a partialdevelopment of the retainer ring and the coil-endsshown in the preceding figures, and

Fig. 4 is a curve diagram.

In the drawings, my invention is shown applied to a'rotor member of aturbo-alternator comprising direct-current exciting windings having aplurality of coil-ends 6 projecting out beyond the rotor core 7' andextending circumferentially around the end of the rotor member, the samebeing retained against centrifugal forces by a re- Some, or all, of thecoil-ends,

V particularly the longest ones which have the longest circumferentialdistance to travel, are

spaced more than the others and are provided with blocking means ofmicartaboard, or the like, as indicated at 10 and 11. These blockingplates are provided with vertically extending channels 12 along theirsides, which communicate with transverse channels 13 across their tops,the latter communicating with holes or perforations 15 which are drilledinto the retaining ring 8'. I

The channels 12 in the side faces of the blocking plates 10 and 11 arein communication with the sides of the adjacent coil-ends 6, and providehigh-velocity streams of air passing over said coil-ends'to cool thesame, as hereinbefore explained. a

These channels are narrow, having a width or 7 depth (measuring axiallyaway from the surface of the coil-end) generally of the order ofone-eighth of an inch or less. As turbo-rotor windings are nowconstructed, it is impossible to space the coil-ends or end turns withsufii- 7 cient accuracy, and so close together, without the use of theblocking plateslO and 11. Fig.

4 shows the effects of the spacers 10 and 11 between the coil-ends 6,these effects being plotted as a function of the ratio of the area ofthe ventilating spaces 12 to the area of the holes 15. The area of theventilating space is the mean cross-sectional area of the air which isflowing radially outward in the channels 12, and it is obtained bymultiplying the channel width by the circumferential length of the same.The corresponding combined widths of the double channel, such as the twochannels 12 of the blocking plate 10, are also plotted as abscissa.

Two sets of curves are shown in Fig. 4. Curves 9o 21 and 22 show thevariation in the amount of heat transferred, for a given exposed area ofthe coil and for a given temperature difference between the coil and theair, for the diiferent ratios of areas, the upper curve 21 being for amachine 05 having a three-inch coil depth and the lower curve 22 beingfor a machine having a seven-inch coil depth. The other two curves 23and 24 show the variation in the volume of air, under the sameconditions.

It would be theoretically desirable to have the ratio of areas and thewidth of ventilating space or channels so small that the maximum heattransfer would be obtained, but reference to Fig. 4 will show that thesevalues of ratio and width 106 together are so small that it isnot, atpresent, considered to be safe practice to approach such dimensions veryclosely, because of the danger of such minute channels becoming quicklyclogged with dirt, and because ofthe physical p0 lating air in theventilating spaces or channels.

The mean velocity of this air should be more than one-tenth of theperipheral velocity of the outer surface of the retaining ring and,preferably, it should be at least of the order of about one-fifth ofsaid peripheral velocity. Thus, in a four-pole 60-cycle machine, of100,000 K. V; A. capacity, the peripheral velocity of a fifty-eightinchretaining ring is 27,300 feet per minute, and

the velocity of the air in the channels 12 is something of the order of5000 to 6000 feet per minute.

It is important to note that the end-coil surfaces which are directlycooled by high-velocity air-streams are defined by blocks or spaces 10and 11, and that those portions of the end-coil surfaces which arenotdirectly cooled by the airstreams are only slightly warmer than thecooled parts, as the distance that theheat flows from the one to theother is short.

Tests have indicated that the introduction of my spacing blocks 10 and11 has resulted in a reduction of the hot-spot temperature-rise, intesting for a considerable overload, from 275 C. to 67 C., with acorresponding large reduction in the average temperature of the winding.

While I have shown my invention in a single form of construction Whichis, at present, the preferred form, it is obvious that I am not limitedto any one precise detail of construction. I desire, therefore, that theappended claims shall be accorded the broadest construction consistentwith their language and the prior art.

I claim as my invention:

1. A rotor member for a dynamo-electric machine, said rotor membercomprising windings having end turns, at least some of the end turnsbeing spaced from each other to provide channels for the flow of air,solid metal retainer rings surrounding said end turns for retaining themagainst centrifugal forces, said retainer rings being perforated topermit the escape of ventilating air for said end turns, the sizes ofthe channels and perforations being such that at least some of the airthat flows in said channels past the end turns and out through theretainer-ring perforations associated therewith has a meancross-sectional area, in said channels, which is less than four timesthe area of the associated perforations.

2. A rotor member for a dynamo-electric machine, said rotor membercomprising windings having end turns, solid metal retainer ringssurrounding said end turns for retaining them against centrifugalforces, said retainer rings being perforated to permit the escape ofventilating air for said end turns and characterized further by narrowchannels between certain of said end turns, said narrow channels havingsuch restricted width that the mean velocity of the ventilating airtherein is more than one-tenth, and of the orderof one-fifth, of theperipheral velocity of the outer surface of the retainer rings.

3. A rotor member for a turbo-dynamo-electric machine, said rotor membercomprising windings having end turns, at least some of the end turnsbeing spaced from each other, solid metal retainer rings surroundingsaid end turns for retaining them against centrifugal forces, saidretainer rings being perforated to permit the escape of ventilatingairfor said end turns and characterized further by spacers between at leastsome of the spaced sides of said end turns, said spacers having channelsin their sides, adjacent to the respective end turns, the relative sizesof the channels of the spacers and the perforations of the retainer ringbeing such that at least some of the air that flows in said channelspast the end turns and out through the retainer-ring perforationsassociated therewith has a mean crosssectional area, in said channels,which is less than four times the area of the associated perforations.

4. A rotor member for a turbo-dynamo-electric machine, said rotor memberhaving windings with end turns, at least some of the end turns beingspaced from each other, solid metal re tainer rings surrounding said endturns for retaining them against centrifugal forces, said retainer ringsbeing perforated to permit the escape of ventilating air for said endturns, and characterized further by spacers between at least some of thespaced sides of said end turns, said spacers having channels in theirsides, adjacent to the respective end turns, said channels being of suchrestricted cross-section that the mean velocity of the air in saidchannels is at least of the order of about one-fifth of the peripheralvelocity of the outer surface of'the retainer rings.

CARL J. FECHHEIMER.

